In this study, we investigate in detail the impact of soluble surfactant on the drag reduction of SHSs in laminar channel flows.
Surfactants are amphiphilic compounds that can be transported by a liquid, adsorb at liquid–gas interfaces and lower the surface tension of these interfaces [1]}.
Transported by the flow along the liquid–gas interface, surfactants can accumulate at stagnation points (liquid–gas–solid contact lines), inducing an adverse Marangoni stress at the interface which increases the drag, thereby negating the drag-reducing effect of the nominally shear-free interface.
